.
.
.
.
.
(Centre of curvature : C) –
, .
C1 C2 .
(Radius of curvature : R) –
(R1R2) .
(Principal axis) –
.
. 7.5
. F1 F2
.
7.5
( ),
(Diverging lense)
7.5 b
(Diverging lense)
:
.
.
,
.
.
:
7.7 AB 2F1
. B BC
F2 CT B
BO OS CT
Bl Bl B .
7.9 PQ F12F1
. P PA
AD . AD
F1 .P
O PO
. PO AF1
P1 P P1
. Q P
Q1 . PQ
P1 Q1 .
(u) (v) (f)
. .
.
.
(Lens formula)
, (O) .
(Frame of Referance) X .
.
1. .
.
2.
.
3. ( )
.
4. ( )
.
5.
.
(Power of a lens)
(P) .
.
. (D) .
(Combination of lenses)
f1 f2
f .
P1 P2
(P)
. P = P1+ P2
(Human eye and working of its lens)
. ( 7.11
). .
.
.
.
.
.
‘ ’ .
.
.
. .
.
.
(Human eye and working of its lens)
(Human eye and working of its lens)
() .
.
.
,
.
(Human eye and working of its lens)
( )
. ( 7.12 )
. ( 7.12 )
.
.
.
.
25 cm .
. .
(Defects of vision and their
corrections)
.
. : .
1. (Nearsightedness/ Myopia)
,
. ,
( 7.13 ).
.
1.
(Nearsightedness/ Myopia)
-
.
.
.
.
.
.
2. (Farsightedness/Hypermetropia)
,
25cm .
. ( 7.14 )
.
2. (Farsightedness/Hypermetropia)
-
.
.
,
.
.
2. (Farsightedness/Hypermetropia)
3. (Presbyopia)
: .
.
.
. -
-
.
(Apparant size of
object)
PQ P1Q1. PQ
(α)
P1 Q1 (β)
PQ P1
Q1 .
(Use of concave lenses)
. , .. :
.
.
. ,
.
.
. :
. :
.
. , :
.
.
(Use of convex lenses)
. (Simple Microscope)
,
. .
(magnifying glass) .
20
. ,
.
.
, ,
. .
.
.
.
.
. (Compound Microscope)
. ,
. .
1. - .
2. - .
.
,
.
. (Telescope)
.
.
.
,
.
, .
?
(Persistance of vision)
.
.
,
.
.
,
.
.
.
. ,
.
.
.
.
(Colour blind) .
.
Drawing a Concave Lens Ray Diagram
S
: Smaller
A
: Upright
L
: In front of F
T
: Virtual
2F F F’’ 2F’
Step 1
Draw a ray parallel to the
principal axis that is refracted
through the principal focus (F).
Step 2 Draw a ray that passes
through the secondary
principal focus (F') and
refracts parallel to the
principal axis.
Step 3 Draw a ray that passes
through the optical center
goes straight through,
without bending.
Drawing a Concave Lens Ray Diagram
S
: Smaller
A
: Upright
L
: In front of F
T
: Virtual
2F F F’’ 2F’
Step 1
Draw a ray parallel to the
principal axis that is refracted
through the principal focus (F).
Step 2 Draw a ray that passes
through the secondary
principal focus (F') and
refracts parallel to the
principal axis.
Step 3 Draw a ray that passes
through the optical center
goes straight through,
without bending.
